Method and apparatus for measuring wavefront aberrations

ABSTRACT

An apparatus and method for measuring wavefront aberrations. A beam splitter separates the aberrated wavefront into two components, mirror arrays focus each of the components to a plurality of discrete lines with the discrete lines of one component having a different orientation than the discrete lines of the other component, and an imaging device detects the discrete lines to determine wavefront aberrations. The method includes separating the wavefront into two components, focusing each of the components into a plurality of discrete lines with the discrete lines of one component having a different orientation than the discrete lines of the other component, and detecting information related to the discrete lines.

FIELD OF THE INVENTION

[0001] The present invention relates generally to optical instrumentsand, more particularly, to a method and apparatus for measuringwavefront aberrations. The present invention is particularly useful, butnot exclusively so, for measuring the optical wavefront in ophthalmicapplications, e.g., measurement of aberrations of the eye, developingcorrective devices such as lenses (e.g., contact, spectacle, andintraocular), and for evaluating the ocular aberrations before, duringand after refractive surgery to improve vision.

BACKGROUND OF THE INVENTION

[0002] The human eye is an optical system employing several lenselements to focus light rays representing images onto the retina withinthe eye. The sharpness of the images produced on the retina is a factorin determining the visual acuity of the eye. Imperfections within thelens and other components and material within the eye, however, maycause the light rays to deviate from a desired path. These deviations,referred to as aberrations, result in blurred images and decreasedvisual acuity. Hence, a method and apparatus for measuring aberrationsis desirable to aid in the correction of such problems.

[0003] One method of detecting aberrations introduced by an eye involvesdetermining the aberrations of light rays exiting from within the eye. Abeam of light directed into the eye as a point on the retina isreflected or scattered back out of the eye as a wavefront, with thewavefront containing aberrations introduced by the eye. By determiningthe propagation direction of discrete portions (i.e., samples) of thewavefront, the aberrations introduced by the eye can be determined andcorrected. In this type of system, increased accuracy in determining theaberrations can be achieved by reducing the size of the samples.

[0004] A general illustration of the generation of a wavefront is shownin FIG. 1. FIG. 1 is a schematic view of a wavefront 10 generated byreflecting a laser beam 12 off of the retina 14 of an eye 16. The laserbeam 12 focuses to a small spot 18 on the retina 14. The retina 14,acting as a diffuse reflector, reflects the laser beam 12, resulting inthe point source wavefront 10. Ideally, the wavefront 10 would berepresented by a spherical or planar wavefront 20. However, aberrationsintroduced by the eye 16 as the wavefront 10 passes out of the eye 16result in an imperfect wavefront, as illustrated by the wavefront 10.The wavefront 10 represents aberrations which lead to defocus,astigmatism, spherical aberrations, coma, and other irregularities.Measuring and correcting these aberrations allow the eye 16 to approachits full potential, i.e., the limits of visual resolution.

[0005]FIG. 2 is an illustration of a prior art apparatus for measuringthe wavefront 10 as illustrated in FIG. 1. By measuring the aberrations,corrective lens can be produced and/or corrective procedures performedto improve vision. In FIG. 2, a laser 22 generates the laser beam 12which is routed to the eye 16 by a beam splitter 24. The laser beam 12forms a spot 18 on the retina 14 of the eye 16. The retina 14 reflectsthe light from the spot 18 to create a point source wavefront 10 whichbecomes aberrated as it passes through the lens and other components andmaterial within the eye 16. The wavefront 10 then passes through thebeam splitter 24 toward a wavefront sensor 26.

[0006] Typical prior art wavefront sensors 26 include either anaberroscope 28 and an imaging plane 30, as illustrated in FIG. 3, or aHartman-Shack sensor 32 and an imaging plane 30, as illustrated in FIG.4. The wavefront sensor 26 samples the wavefront 10 by passing thewavefront 10 through the aberroscope 28 or the Hartman-Shack sensor 32,resulting in the wavefront 10 producing an array of spots on the imagingplane 30. Each spot on the imaging plane 30 represents a portion of thewavefront 10, with smaller portions enabling the aberrations to bedetermined with greater accuracy. Generally, the imaging plane 30 is acharge coupled device (CCD) camera. By comparing the array of spotsproduced on the imaging plane 30 by the wavefront 10 with a referencearray of spots corresponding to the wavefront of an ideal eye, theaberrations introduced by the eye 16 can be computed.

[0007] An example of a Hartman-Shack system described in U.S. Pat. No.6,095,651 to Williams et al., entitled Method and Apparatus forImproving Vision and the Resolution of Retinal Images, filed on Jul. 2,1999, is incorporated herein by reference.

[0008] The resolution of the aberrations in such prior art devices,however, is limited by the sub-aperture spacing 34 and the sub-aperturesize 36 in an aberroscope 28 (see FIG. 3), and by the lensletsub-aperture spacing 38, and focal length, in a Hartman-Shack sensor 32(see FIG. 4). In addition, since each area is represented by a singlespot, the amount of information captured for each area is limited. Also,because of foldover, reductions to sub-aperture spacing 34 and size 36and lenslet sub-aperture spacing 38, the capabilities to obtain moredetailed information are limited.

[0009] Foldover occurs in an aberroscope sensor 28, for example, whentwo or more spots 40A, 40B, and 40C on imaging plane 30 overlap, therebyleading to confusion between adjacent sub-aperture spots. Similarly,foldover occurs in Hartman-Shack sensors 32 when two or more spots 42A,42B, 42C, and 42D on imaging plane 30 overlap. Foldover may result froma sub-aperture spacing 34, sub-aperture size 36, or lenslet spacing 38which is too small; a high degree of aberration; or a combination ofthese conditions. Hence, the sub-aperture spacing 34 and sub-aperturesize 36 in the aberroscope 28, and the lenslet sub-aperture spacing 38,and focal length in the Hartman-Shack sensor 32 must be selected toachieve good spatial resolution while enabling the measurement of largeaberrations. Accordingly, the ability to measure a high degree ofaberration comes at the expense of spatial resolution and/or dynamicrange and vice versa.

[0010] The constraints imposed by the aberroscope and Hartman-Shackapproaches limit the effectiveness of these systems for measuringaberrations with a high degree of accuracy. These limitations preventoptical systems from achieving their full potential. Accordingly,ophthalmic devices and methods which can measure aberrations with a highdegree of accuracy would be useful.

SUMMARY OF THE INVENTION

[0011] The present invention provides for an apparatus and method fordetermining the aberrations of a wavefront with a high degree ofaccuracy. The apparatus includes a beam splitter for separating thewavefront into two components, mirror arrays for focusing each of thecomponents to a plurality of discrete lines with the discrete lines ofone component having a different orientation than the discrete lines ofthe other component, and an imaging device for detecting the discretelines to determine wavefront aberrations. The method includes separatingthe wavefront into two components, focusing each of the components intoa plurality of discrete lines with the discrete lines of one componenthaving a different orientation than the discrete lines of the othercomponent, and detecting information related to the discrete lines.

[0012] By generating discrete lines which represent the wavefront, theapparatus and method of the present invention are capable of measuringthe wavefront with a high degree of accuracy. Since each of theplurality of discrete lines have a different orientation, the pluralityof discrete line essentially represent the wavefront as a grid. Thepresent invention is able to provide more accurate information thanprior art systems since the grid lines of the present invention providemore information for each section of the grid than the spots which wouldbe generated by prior art systems to represent equivalent areas.

[0013] In a system for measuring the wavefront of an eye, the wavefrontoriginates as a point source within the eye. The point source isgenerated by directing a beam of radiation (e.g., a laser) into the eyeand scattering or reflecting the beam. A beam splitter disposed in thepath of the laser beam directs the laser beam into the eye. The retinaof the eye functions as a diffuse reflector for reflecting or scatteringthe beam. The wavefront resulting from the point source passes out ofthe eye and through the beam splitter to the wavefront sensor of thepresent invention. The wavefront sensor measures the aberrations of thewavefront introduced by the eye. Aberrations are then computed by aprocessor coupled to the wavefront sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic of a wave produced by a laser beam reflectedby the retina of an eye;

[0015]FIG. 2 is a schematic of a prior art apparatus for measuringaberrations introduced by an eye;

[0016]FIG. 3 is a schematic of an aberroscope for use in a prior artapparatus for measuring aberrations;

[0017]FIG. 4 is a schematic of a Hartman-Shack lenslet array for use ina prior art apparatus for measuring aberrations;

[0018]FIG. 5 is a schematic of an apparatus for measuring aberrations ina wavefront introduced by an optical system in accordance with thepresent invention;

[0019]FIG. 6 is an illustrative schematic of a mirror array reflectingand focusing a wavefront for use in the apparatus of FIG. 5 inaccordance with the present invention;

[0020]FIG. 6A is a schematic illustrating a plurality of discrete linesof one orientation displayed on an imaging surface resulting from onemirror array of FIG. 5;

[0021]FIG. 6B is a schematic illustrating a plurality of discrete linesof another orientation displayed on an imaging surface resulting fromthe other mirror array of FIG. 5; and

[0022]FIG. 6C is a schematic illustrating the combination of theplurality of discrete lines of FIG. 6A with the plurality of discretelines of FIG. 6B.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Illustrated in FIG. 5 is a preferred embodiment of a wavefrontmeasuring apparatus 100 in accordance with the present invention formeasuring the aberrations of an optical system 102, which here is an eye104. In a general overview, a beam 106 is generated and directed intothe eye 104. The beam 106 is reflected as a wavefront 108 which passesout of the eye 104 and is then directed toward a wavefront detection(WD) device 110 for detecting aberrations within the wavefront 108. Inthe WD device 110, the wavefront 108 is passed toward a WD beam splitter112 where the wavefront 108 is separated into two components. One of thewavefront components is reflected toward a first mirror array 114A andthe other component is passed through the beam splitter 114 toward asecond mirror array 114B. The mirror arrays 114A,114B divide, reflect,and focus the wavefront component incident on their respective surfacesto a plurality of discrete lines which are ultimately detected by animaging device 116. Other components within the WD device 110 are usedfor routing the two wavefront components. The present invention is nowdescribed in more detail.

[0024] In the preferred embodiment, and for purposes of illustration, aradiation source 118 generates the beam 106, and a wavefront generation(WG) beam splitter 120 directs the beam 106 toward the eye 104, andthereafter directs the resultant wavefront 108 out of the eye 104 towardthe WD device 110. In the preferred embodiment, the wavefront 108 islinearly polarized. Alternatively, the wavefront 108 may be unpolarizedor circularly polarized.

[0025] The illustrated optical system 102 is the eye 104. Alternatively,the optical system 102 may include a reflective surface and a contactlens or eyeglass, an eye and a contact lens or eyeglass, a telescope, amicroscope, or other type of optical system to be analyzed. In theillustrated embodiment, the beam 106 from the radiation source 108focuses to a spot 122 on the retina 124 of the eye 104. A focusing lensor system of lenses may be used in the path of the beam 106 to accountfor defocus and/or astigmatism of the eye 104. The retina 124, acting asa diffuse reflector, effectively becomes the source for light leavingthe eye 104, thereby creating the wavefront 108. Aberrations due toimperfections within the eye 104 affect the wavefront 108.

[0026] The radiation source 110 is a device capable of generating afocused beam of photons, and is preferably a laser. Alternativeradiation sources 110 include a laser diode, super-luminescent diode, oressentially any radiation device capable of generating a focused beam asmay be known in the art. Additionally, the radiation source 110 mayinclude a spatial filter for correcting noise associated with theradiation source 110. In the preferred embodiment, the beam 106generated by the radiation source 110 is polarized.

[0027] The WG beam splitter 120 is capable of selectively passing anddirecting beams. Here, the WG beam splitter 120 is configured to reflectthe beam 106 toward the optical system 102 and to pass the wavefront 108projecting from the optical system 102 toward the WD device 110unaltered. In the preferred embodiment, the WG beam splitter 120 is apolarizing beam splitter which passes light polarized in one directionand reflects light polarized in the other direction. A common namingconvention is to refer to light polarized in one direction as“p”-polarized light and light polarized at a 90 degree angle to the“p”-polarized light as “s”-polarized light. Once the WG beam splitter120 is aligned, the axis which passes the “p”-polarized light is calledthe “p” axis. The details which enable the WG beam splitter 120 todirect light appropriately for use in the preferred embodiment arediscussed below.

[0028] The quarter-wave plate 126 is an optical component which assistssystems 100 of the type illustrated here, i.e. systems which usepolarization for routing beams, to distinguish between beams enteringthe eye 104 and those leaving the eye 104. Prior to reaching the plate126, the beam 106 is linearly polarized (e.g., in an “s” direction).After passing through the plate 126, the beam 106 is circularlypolarized in one direction. The circularly polarized beam 106 is focusedto a spot 122 on the retina 124 of the eye 104. The wavefront 108 isproduced by reflecting the circularly polarized beam 106 off of theretina 124. It is understood by those skilled in the art that thewavefront 108 will be circularly polarized in a direction opposite tothat of the beam 106 due to reflection by the retina 124. After thewavefront 108 emanates from the eye 104, the quarter-wave plate 126 willlinearly polarize the circularly polarized wavefront 108 to produce alinearly polarized wavefront 108 (e.g., in a “p” direction) having anorientation that is 90 degrees different from the linear polarization ofthe beam 106 which entered the eye 104.

[0029] In an illustrative example, the WG beam splitter 120 reflects alinearly “s”-polarized beam 106 (i.e., polarized at a 90 degree angle tothe p-axis of the WG beam, splitter 120) toward the eye 104. Thelinearly polarized wavefront 108 which exits the eye 104 is“p”-polarized (i.e., polarized on axis with the p-axis of the WG beamsplitter 120) due to the quarter-wave plate 126 and reflection withinthe eye 104. Since the polarization of the wavefront 108 is on axis withthe p-axis of the WG beam splitter 120, the WG beam splitter 120 willallow the wavefront 108 to pass unaltered toward the WD device 110.

[0030] One or more optical devices, such as lenses 128, are positionedwithin the wavefront measurement apparatus 100 to direct the wavefront108 between the eye 104 and the wavefront detection device 110. Theypreserve the propagation directions of the waves which make up thewavefront 108 as they are passed from the eye 104 to the WD device 110.Such devices are well known in the art.

[0031] In the preferred embodiment, the wavefront detection (WD) device110 includes a WD beam splitter 112, two mirror arrays 114A, B, twoquarter-wave plates 130A, B, a half-wave plate 132, and an imagingdevice 116. The WD beam splitter 112 separates an incoming wavefront 108into two components 108A and 108B with each of the componentsrepresentative of the entire wavefront 108. The WD beam splitter 112reflects approximately half the intensity of the wavefront 108 as thewavefront 108A (e.g., as light polarized in an “s” direction) toward themirror array 114A, and will pass the other half of the intensity of thewavefront 108 as the wavefront 108B (e.g., as light polarized in a “p”direction) toward the mirror array 114B.

[0032] It is understood by those skilled in the art that light polarizedin a given direction can be broken down into two components by orientingthe axis of a polarized beam splitter and the polarization axis of thepolarized light at a 45 degree angle relative to one another. In thisorientation, the polarized beam splitter will reflect half of theintensity of the polarized light and transmit half of the intensity ofthe polarized light. For example, the wavefront 108 can be broken downinto two polarized components (e.g., “s” and “p” polarized light) byorienting the axis of the WD beam splitter 112 and the polarization ofthe wavefront 108 relative to one another such that the WD beam splitter112 reflects “s”-polarized light as the wavefront 108A and passes“p”-polarized light as the wavefront 108B.

[0033] In order to orient the axis of the WD beam splitter 112 and thepolarization of the wavefront 108 at a 45 degree angle relative to oneanother, the polarization of the wavefront 108 can be rotated relativeto the axis of the WD beam splitter 112 and/or the axis of the WD beamsplitter 112 can be rotated relative to the polarization of thewavefront 108. In the preferred embodiment, a known half-wave plate 132is used to change the polarization axis of the wavefront 108 by 45degrees to obtain “p*”-polarized light. If the axis of the WD beamsplitter 112 is aligned to pass “p”-polarized light and to reflect “s”polarized light, the “p*”-polarized light can be divided into twocomponents (e.g., “s” and “p”) since the “p*”-polarized wavefront 108 isoriented at a 45 degree angle to the “p” polarization axis of the WDbeam splitter 112. In an alternative embodiment, the axis of the WD beamsplitter is rotated by 45 degrees, along with the other componentswithin the WD device 110, relative to the wavefront 108, therebyremoving the need for the half-wave plate 132. In this arrangement, theWD beam splitter 112 will pass a portion of the intensity of the “p”polarized light as “p*” polarized light and reflect the remainingintensity of the “p” polarized light as “s*” polarized light.

[0034] In addition, it will be understood that if the wavefront 108 ismade up of circularly polarized light or unpolarized light, theorientation of the WD beam splitter 112 will be irrelevant as circularlypolarized light and unpolarized light can each be conceptually brokeninto two components regardless of the orientation of the axis of the WDbeam splitter 112. The circularly polarized light and the unpolarizedlight can each be broken down into two components regardless of theorientation of the WD beam splitter 112 because they each contain anequal distribution of light which allows them to be split into two equalcomponents at right angles to one another. Therefore, for circularlypolarized light or unpolarized light, the WD beam splitter 112 willreflect half the light as “s”-polarized light toward the mirror array114A and pass half the light as “p”-polarized light toward the mirrorarray 114B regardless of the orientation of the WD beam splitter 112 andwithout the use of a half-wave plate 132.

[0035] With further reference to FIG. 5, the mirror arrays 114A, Bdivide, reflect, and focus light incident on their surfaces to aplurality of discrete lines. Each of the mirror arrays 114A, B are madeup of a plurality of cylindrical mirrors 134, with each of thecylindrical mirrors 134 corresponding to a rectangular portion of thewavefront 108. Preferably, the cylindrical mirrors 134 are formed of aplurality of reflective parallel grooves. The mirror arrays 114A, B areoriented relative to one another such that the rectangular portions andthe discrete lines produced from the rectangular portions by one mirrorarray 114A are distinguishable from the rectangular portions and thediscrete lines produced from the rectangular portions by the othermirror array 114B.

[0036]FIG. 6 illustrates the operation of one of the mirror arrays 114A,with the other mirror array 114B operating in a similar manner. For awavefront 108A traveling toward the mirror array 114A, the cylindricalmirrors 134 will divide the wavefront 108A which is incident on theirrespective surfaces into wavefront portions 136. The cylindrical mirrorarray 114A reflects the wavefront portions 136 and focus them to aplurality of discrete lines 138A (represented by spots on imaging device116). Preferably, the cylindrical mirror array 114A focuses theplurality of discrete lines on an imaging surface 116A (represented bythe bottom edge of the imaging device 116).

[0037] In the preferred embodiment, illustrated in FIGS. 6A and 6B, themirror arrays 114A, B are oriented such that one of the mirror arrays114A divides the wavefront 108A into a plurality of vertical rectangularportion which are reflected and focused to a plurality of verticaldiscrete lines 138A (FIG. 6A) on the imaging surface 116A, and the othermirror array 114B divides the wavefront 108B into a plurality ofhorizontal rectangular portions which are reflected and focused to aplurality of horizontal vertical lines 138B (FIG. 6B) on the imagingsurface 116A. Preferably, the light which generates the discrete lines138A, B is directed towards the imaging surface 116A by the WD beamsplitter 112, discussed in detail below. In the preferred embodiment,the plurality of discrete vertical lines 138A and the plurality ofdiscrete horizontal lines 138B are focused onto the same imaging surface116A to form a grid which is representative of the wavefront 108, asillustrated in FIG. 6C. In an alternative embodiment, each of theplurality of discrete lines may be focused to a different imagingdevice.

[0038] The imaging device 116 (FIG. 5) is capable of precisely detectingthe location of energy incident to an imaging plane 116A. Preferably,the imaging device 116 is a charge coupled device (CCD) camera which iscapable of converting energy incident to an imaging plane into a digitalrepresentation. Charge coupled devices are well known and a suitabledevice for use with the present invention would be readily apparent tothose skilled in the art.

[0039] The aberrations which are introduced by the optical system 102affect the discrete lines 138A, B. For an aberration free optical system102, the discrete lines 138A, B would be substantially straight.Aberrations within the optical system 102, however, cause the discretelines 138A, B to deviate from being substantially straight. Theaberrations of the optical system 102 can be determined by measuring thedifference in location between individual points on a discrete line138A, 138B produced from an optical system 102 and corresponding pointson the substantially straight discrete line 138A, 138B for an aberrationfree optical system 102, and calculating the aberration which wouldproduce the measured difference for each point. The determinedaberrations for the individual points are then combined to determine theaberrations of the optical system 102.

[0040] Methods for calculating aberrations based on the differencebetween discrete lines 138A, B produced by the optical system 102 andthe substantially straight discrete lines 138A, B produced by anaberration free system 102 will be readily apparent to those in the art.The discrete lines 138A, B used to represent the wavefront 108 allow thewavefront 108 to be analyzed in greater detail than in prior art systemswhich generate a finite number of spots to represent the wavefront 108,because more reference locations are available for performingcalculations.

[0041] The quarter-wave plates 140A, B modify their respective wavefrontcomponents 108A, B as described below so that they can be recombined atthe WD beam splitter 112 for measurement by a single imaging device 116.With reference to FIG. 5, a polarized WD beam splitter 112 is used forpurposes of the present illustration. As previously explained, thewavefront 108 coming from the eye 104 is split into component waves 108Aand 108B by the WD beam splitter 112, the wavefront component 108A beingpolarized in the “s” direction and thus reflecting downward toward themirror array 114A, the wavefront component 108B being polarized in the“p” direction and thus passing through the WD beam splitter 112 towardthe mirror array 114B. After reflecting from the WD beam splitter 112,the wavefront component 108A passes through the quarter-wave plate 140Awhich changes the “p” linearly polarized wavefront component 108A to acircularly polarized wavefront 108A. When the circularly polarizedwavefront 108A is reflected by the mirror array 114A, the circularpolarization is reversed. Upon passing back through the quarter-waveplate 140A, towards the WD beam splitter 112, the reversed circularlypolarized wavefront 108A will be changed to a linearly polarizedwavefront component 108A in the “p” direction, as opposed to the “s”direction, due to the reversed circular polarization. Being now linearlypolarized in the “p” direction, the wavefront component 108A will passthrough the beam splitter 112 towards the imaging device 116.

[0042] In a similar manner, the “p” linearly polarized wavefrontcomponent 108B passing through the WD beam splitter 112 towards themirror array 114B passes through the quarter-wave plate 140B whichchanges the “p” linearly polarized wavefront component 108B to acircularly polarized wavefront 126B. The reflection of this wavefront108B by the mirror array 114B then reverses the circular polarization,and, upon passing back through the quarter-wave plate 140B towards theWD beam splitter 112 is changed to an “s” linearly polarized wavefrontcomponent 108B which is now reflected by the WD beam splitter 112 towardthe imaging plane 116, and thereby recombined with the wavefrontcomponent 108A.

[0043] In an alternative embodiment (not shown), multiple imagingdevices 116 can be used, thereby removing the need to recombine thewavefront components 108A, 108B. Therefore, according to thisembodiment, the quarter-wave plates may be eliminated without departingfrom the spirit and scope of the present invention.

[0044] The processor 142 receives information from the imaging device116 and analyzes the information to compute the aberrations. Theinformation may be stored in a storage register prior to processing byprocessor 142 or may be processed immediately. It is apparent to thoseskilled in the art that the receipt of information from the imagingdevice 116 and the processing of information may be performed by asingle processor or divided among a plurality of processors.

[0045] In accordance with an embodiment of the present invention, anaberration correction device 144 is coupled to the processor 142.Alternatively, information calculated by the processor 142 may be storedon a hard drive, diskette, server, compact disc, digital versatile disc,or essentially any device capable of storing information. The storedinformation is then passed to an aberration correction device 144. Theaberration correction device 144 includes a known lens grinder, contactlens manufacturing system, surgical laser system, or other opticalsystem correction device. In a surgical laser system, a laser can beoptically positioned relative to the WG beam splitter 120 to direct alaser cutting beam toward the cornea of the eye 104, in a manner wellknown in the art, for the purpose of performing ophthalmic surgery.

[0046] For illustrative purposes, the present invention has beendescribed in terms of measuring wavefront aberrations introduced by ahuman eye. However, it will be readily apparent to those skilled in theart that the present invention can be used to measure aberrationscreated by other optical systems, e.g. eyeglasses, telescopes,binoculars, monoculars, contact lenses, non-human eyes, or combinationof these systems.

[0047] Having thus described a few particular embodiments of theinvention, various alterations, modifications, and improvements willreadily occur to those skilled in the art. Such alterations,modifications and improvements as are made obvious by this disclosureare intended to be part of this description though not expressly statedherein, and are intended to be within the spirit and scope of theinvention. Accordingly, the foregoing description is by way of exampleonly, and not limiting. The invention is limited only as defined in thefollowing claims and equivalents thereto.

What is claimed is
 1. A sensor for detecting aberrations of a wavefrontemitted from an optical system, said sensor comprising: a beam splitterfor receiving the wavefront and separating the wavefront into a firstcomponent having a first polarization and a second component having asecond polarization, said first polarization being distinguishable fromsaid second polarization; a first mirror array reflecting and focusingsaid first component to a first plurality of discrete lines having afirst orientation; a second mirror array for reflecting and focusingsaid second component to a second plurality of discrete lines having asecond orientation different from said first orientation; and an imagingdevice for detecting said first plurality of discrete lines and saidsecond plurality of discrete lines.
 2. A sensor in accordance with claim1, wherein said first mirror array and said second mirror array areconfigured to orient said first plurality of discrete linessubstantially perpendicular to said second plurality of discrete lines.3. A sensor in accordance with claim 2, wherein said imaging device is acharge coupled device (CCD).
 4. A sensor in accordance with claim 3,further comprising a processor for analyzing said first and secondpluralities of discrete lines produced on said CCD.
 5. A sensor inaccordance with claim 1, further comprising: a first quarter-wave plateoptically positioned between said beam splitter and said first mirrorarray to convert said first component from linear polarization of afirst propagation direction to circular polarization upon the passing ofsaid first component through said first quarter-wave plate to said firstmirror array and to convert said first component from circularpolarization to linear polarization of a second propagation directionupon the passing of said first component through said first quarter-waveplate from said first mirror array; and a second quarter-wave plateoptically positioned between said beam splitter and said second mirrorarray to convert said second component from linear polarization of athird propagation direction to circular polarization upon the passing ofsaid second component through said second quarter-wave plate to saidsecond mirror array and to convert said second component from circularpolarization to linear polarization of a fourth propagation directionupon the passing of said second component through said secondquarter-wave plate from said second mirror array.
 6. A sensor inaccordance with claim 5, wherein said beam splitter is configured tocombine said first and second components after reflection by said firstand second mirror arrays, respectively.
 7. A sensor in accordance withclaim 6, wherein said beam splitter is a polarizing beam splitterconfigured to pass said first component linearly polarized in said firstpropagation direction and said second component linearly polarized insaid fourth propagation direction, and to reflect said first componentlinearly polarized in said second propagation direction and said secondcomponent linearly polarized in said third propagation direction.
 8. Asensor in accordance with claim 7, wherein said first propagationdirection and said fourth propagation direction are the same, and saidsecond propagation direction and said third propagation direction arethe same.
 9. A sensor in accordance with claim 1, wherein said imagingdevice comprises a single imaging device for detecting both said firstplurality of discrete lines and said second plurality of discrete lines.10. An apparatus for measuring aberrations of a wavefront emitted froman optical system, comprising: a beam splitter for receiving andseparating the wavefront into a first component having a firstpolarization and a second component having a second polarization, saidfirst polarization being distinguishable from said second polarization;a first mirror array for reflecting and focusing said first component toa first plurality of discrete lines having a first orientation; a secondmirror array for reflecting and focusing said second component to asecond plurality of discrete lines having a second orientation differentfrom said first orientation; and an imaging device for detecting saidfirst plurality of discrete lines and said second plurality of discretelines; and a processor for computing wavefront aberrations from thedetected information received from said imaging device.
 11. An apparatusin accordance with claim 10, further comprising: a radiation source forgenerating a beam to be directed to the optical system to produce thewavefront.
 12. An apparatus in accordance with claim 10, furthercomprising: a first quarter-wave plate positioned between said beamsplitter and said first mirror array to convert said first componentfrom linear polarization to circular polarization upon the passing ofsaid first component through said first quarter-wave plate to said firstmirror array and to convert said first component from circularpolarization to linear polarization upon the passing of said firstcomponent through said first quarter-wave plate from said first mirrorarray; and a second quarter-wave plate positioned between said beamsplitter and said second mirror array to convert said second componentfrom linear polarization to circular polarization upon the passing ofsaid second component through said second quarter-wave plate to saidsecond mirror array and to convert said second component from circularpolarization to linear polarization upon the passing of said secondcomponent through said second quarter-wave plate from said second mirrorarray.
 13. An apparatus in accordance with claim 10, wherein thewavefront is linearly polarized.
 14. An apparatus in accordance withclaim 13, further comprising: a half-wave plate positioned between thewavefront and said beam splitter for altering the linear polarizationaxis of the wavefront.
 15. An apparatus in accordance with claim 10,wherein the wavefront is non-polarized.
 16. An apparatus in accordancewith claim 10, wherein the wavefront is circularly polarized.
 17. Amethod for measuring a wavefront emitted from an eye comprising thesteps of: (a) separating the wavefront into a first component and asecond component; (b) focusing said first component to a first series ofdiscrete lines having a first orientation, and focusing said secondcomponent to a second series of discrete lines having a secondorientation, said second orientation being different from said firstorientation; and (c) detecting information related to said first seriesof discrete lines and said second series of discrete lines fordetermining the aberrations of the wavefront.
 18. A method in accordancewith claim 17, wherein step (a) comprises separating the wavefront intotwo polarized wavefronts having different polarizations.
 19. A method inaccordance with claim 18, wherein said focusing step comprises focusingone of said polarized wavefronts into said first series of discretelines and focusing the other one of said polarized wavefronts into saidsecond series of discrete lines, said discrete lines for one of saidpolarized wavefronts being substantially perpendicular to said discretelines of the other.
 20. A method in accordance with claim 19, whereinstep (b) further comprises combining said first component and saidsecond component.
 21. The method of claim 20, wherein said separatingand combining steps are performed by a beam splitter.
 22. The method ofclaim 21: wherein said separating step separates the wavefront into afirst intermediate wavefront having a first linear polarization togenerate said first component and a second intermediate wavefront havinga second linear polarization different from said first linearpolarization to generate said second component; further comprising thestep of, (a1) converting said first linear polarization to a firstcircular polarization and said second linear polarization to a secondcircular polarization between said separating step (a) and said focusingstep (b); wherein step (b) further comprises the step of reflecting saidfirst component and said second component, said reflecting stepconverting said first circular polarization to a third circularpolarization of an opposite direction than said first circularpolarization and converting said second circular polarization to afourth circular polarization of an opposite direction than said secondcircular polarization; further comprising the step of, (b1) convertingsaid third circular polarization to a third linear polarization andconverting said fourth circular polarization to a fourth linearpolarization between said reflecting and combining of step (b), whereinsaid third linear polarization is substantially the same as said secondlinear polarization and said fourth linear polarization is substantiallythe same as said first linear polarization; and wherein said combiningstep comprises combining said first component having said third linearpolarization with said second component having said fourth linearpolarization.
 23. A method in accordance with claim 17, furthercomprising the step of: analyzing the detected information to determinethe wavefront aberrations.
 24. A method in accordance with claim 23,wherein said analyzing step comprises: comparing information obtainedduring said detecting step with known values for an aberration freewavefront; and calculating the aberration of the wavefront.